1. Field of the Invention
The present invention relates to a novel organic compound and an organic light-emitting device employing the same.
2. Related Background Art
An organic light-emitting device is a device in which a thin film containing a fluorescent organic compound or a phosphorescent organic compound is sandwiched between an anode and a cathode, wherein an exciton is generated from the fluorescent compound or phosphorescent compound by injection of electrons and holes from each electrode, and light is radiated from the exciton when the exciton returns to a ground state, whereby the light is utilized as the light to be emitted from the device.
A study conducted by Eastman Kodak Company in 1987 (Appl. Phys. Lett. 51, 913 (1987)) reported light emission in the order of 1,000 cd/m2 at an applied voltage of about 10 V, from a separated-function type device having two-layer structure in which an anode is made of ITO and a cathode is made of magnesium-silver alloy, an aluminum quinolinol complex is used as both of an electron-transporting material and a light-emitting material and also a triphenylamine derivative is used as a hole-transporting material. Related patents include U.S. Pat. Nos. 4,539,507, 4,720,432, and 4,885,211.
In addition, light emission at spectra ranging from ultraviolet through infrared is allowed by changing the kind of the fluorescent organic compound. Recently, therefore, various compounds have been studied extensively and described in, for example, U.S. Pat. Nos. 5,151,629, 5,409,783 and 5,382,477, and Japanese Patent Application Laid-Open Nos. H02-247278, H03-255190, H05-202356, H09-202878 and H09-227576.
Furthermore, in addition to organic light-emitting devices using low molecular weight materials as described above, an organic light-emitting device using a conjugated polymer has been reported by a group at Cambridge University (Nature, 347, 539 (1990)). In this report, a film is formed with polyphenylene vinylene (PPV) in a coating system and confirmed light emission from a monolayer. Patents relating to an organic light-emitting device using a conjugated polymer include U.S. Pat. Nos. 5,247,190, 5,514,878, 5,672,678, and Japanese Patent Application Laid-Open Nos. H04-145192 and H05-247460.
In recent years, many studies have been made to utilize energy in a triplet state for electroluminescence by using a phosphorescent compound as the light-emitting material. A high emission efficiency exhibited by an organic light-emitting device using an iridium complex as the light-emitting material has been reported by a group at Princeton University (Nature 395, 151 (1998)). Patents relating to an organic light-emitting device using such a transition element-containing phosphorescent compound include U.S. Pat. Nos. 6,303,238 and 6,579,632.
However, such transition element-containing phosphorescent compounds have low thermal resistance, and therefore possess drawbacks such as susceptibility to thermal decomposition during vacuum deposition when producing an organic light-emitting device, and insufficient durability of the organic light-emitting device. Also, such phosphorescent compounds can only emit phosphorescence. No compounds are known which can simultaneously emit fluorescence and phosphorescence by itself.